When assembling a big block, how crucial is THIS ?

[Kern Dog]

Cam plug depth.
Yeah, not a real exciting topic but I'm curious. Here is the depth I had in my 440/493, as noted when I pulled it in 2022 to rebuild.

You can see, the edge of the plug is near the edge of the hole in the block.

When I knocked in the new plug after getting the engine back from the machine shop, without even thinking, I drove the new one in deeper.

For the record, here is one cam that was in the engine for awhile in the first two pictures. This one did not go bad.

It seems like the wear marks are toward the rear of each lobe. I thought that cam lobes were tapered to push the cam rearward. Wouldn't that mean that the wear marks should have been toward the front edges of the lobes?

This cam you see is in my engine now but I'm looking to swap to a roller cam.
My main question here is....How crucial is the depth of the cam plug in regards to fore/aft camshaft placement? Roller cams need a button to limit forward movement and I'm assuming the rearward movement is limited by the cam plug.
What happens if that cam plug is either in too shallow or too deep?

 

[Geoff 2]

The oil pump drive/load is pushing the cam back. The lobe/lifter orientation is to push forward & counteract that force.

Cam plug. Not so far in that it contacts the cam. Use silicon to seal it. It is only subject to a small amount of blowby force.

 

[Kern Dog]

Is safe to assume that the camshaft does not make contact with the plug ever?
I could do a mock up tomorrow with stuff that I have out in the shop but this is something that I've never heard anyone discuss.
My concern is related to the upcoming cam swap due to it being a roller design.

 

[Geoff 2]

No contact....unless the plug is pressed in too far. Would have to see a 440 block to see if that is possible, some engines it is IMpossible.

 

[69B7RR]

If it helps, this is the depth measurement of my original 383 cam plug. I knocked in the new one until it squared & bottomed out against the inner block shoulder. The after install measurement was the same.

 

[Kern Dog]

Thank you. I forgot that there is a step in the diameter of the hole.

 

[69B7RR]

Thank you. I forgot that there is a step in the diameter of the hole.

Glad it helped. Your informative posts have helped me many times in the past.

 

[Kern Dog]

The oil pump drive/load is pushing the cam back.

Okay, if so, what stops the cam from contacting the plug at the bell housing end?
The cam button stops forward travel but what stops it rearward ?

 

[padam]

The timing sprocket contacts the front of the block.

 

[KozmicKuda]

It is my understanding that tapered lobes cause the lifters to rotate to equalize wear. Obviously flat tapped only.

 

[RemCharger]

Okay, if so, what stops the cam from contacting the plug at the bell housing end?
The cam button stops forward travel but what stops it rearward ?

The timing sprocket contacts the front of the block.

That's what the Torrington bearing is for discussed in the other thread.

 

[toolmanmike]

Are you sure that's the right cam plug? Small blocks use a dished plug expanded by denting in the center. it seats against the step in the cam bore. No, I guess not. It looks like a shallow freeze plug in the kits from Mancini.

 

[Badvert65]

What sort of cam button will you be using?

 

[HawkRod]

Are you sure that's the right cam plug? Small blocks use a dished plug expanded by denting in the center. it seats against the step in the cam bore. No, I guess not. It looks like a shallow freeze plug in the kits from Mancini.

View attachment 1808552

Mike: there are two types: The dished, as in pictures by Kern and 67B7RR, and the expanding type (not sure of their "formal" name), where you whack the center with a punch and expand it out. I've used both.

As stated above, the purpose is merely to plug a hole and avoid oil leaking out, but the cam cannot touch the plug - this would be bad.

 

[69Bee]

Are you sure that's the right cam plug? Small blocks use a dished plug expanded by denting in the center. it seats against the step in the cam bore. No, I guess not. It looks like a shallow freeze plug in the kits from Mancini.

View attachment 1808552

All BB's us a cup plug as far as I have seen. I use Loc-Tite 540 (PN#54041) to seal it. This is some great stuff, albeit quite expensive. SB's use either a flat plug or the formed plug (EPC203). Early Hemi's and Flat Head 6 cyls plugs are flat plugs. The plug you show in your pic was installed incorrectly. Too small of a socket or bar was used and pushed the center past the center. This is how they are removed, smack them in the center to relieve tension, and they will come right out. The plug is concave, and fits the bore, but when the plug is flattened, it squeezes it tighter into the bore sides. I also use the loc-Tite product to seal these. I use a larger diameter aluminum bar that is slightly convex in the center to drive the flat plugs. The convex shape does not push the center in and flattens the rest of the plug. Without the correct original tool, which I have never seen, they can surely be a bitch to install correctly.

Loc-Tite: Henkel 54041 LOCTITE® 540™ Blue Retaining Compound - 250 mL (8.45 oz) Bottle - 10/Case

Cam Plug: Dorman 555-123 Cam Plug | 2863071 EPC203

 

[1 Wild R/T]

FWIW the convex plugs are called Welch plugs..

 

[Kern Dog]

The timing sprocket contacts the front of the block.

That's what the Torrington bearing is for discussed in the other thread.

Ahhhh. Now THAT clears it up. Thank you!

What sort of cam button will you be using?

I don't know. I'm just learning about this stuff.

 

[wingman]

I think you're fine. But if you are worried about it (even a little) just knock it out and put in another one. They're like $5 right?
Easy to get to now. Very hard to get to later.
Remember to use sealant.